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                        <h1>go-micro 使用熔断器中间件</h1>
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                <h1><span id="go-micro-使用熔断器中间件">go-micro 使用熔断器中间件</span></h1>
<h2><span id="依赖">依赖</span></h2>
<ul>
<li>micro/go-micro/client</li>
<li>afex/hystrix-go/hystrix</li>
</ul>
<h2><span id="代码amp说明">代码&amp;说明</span></h2>
<p>在 go 微服务 Demo 的代码中新建 wrappers 文件夹，里面新建 productWrapper.go 文件</p>
<h3><span id="productwrappergo">productWrapper.go</span></h3>
<figure class="highlight go"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br><span class="line">46</span><br><span class="line">47</span><br><span class="line">48</span><br><span class="line">49</span><br><span class="line">50</span><br><span class="line">51</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">package</span> wrappers</span><br><span class="line"></span><br><span class="line"><span class="keyword">import</span> (</span><br><span class="line">	<span class="string">"context"</span></span><br><span class="line">	<span class="string">"go-micro-ginClient/services"</span></span><br><span class="line">	<span class="string">"strconv"</span></span><br><span class="line"></span><br><span class="line">	<span class="string">"github.com/afex/hystrix-go/hystrix"</span></span><br><span class="line">	<span class="string">"github.com/micro/go-micro/client"</span></span><br><span class="line">)</span><br><span class="line"></span><br><span class="line"><span class="comment">// 新建商品信息</span></span><br><span class="line"><span class="function"><span class="keyword">func</span> <span class="title">NewProduct</span><span class="params">(id <span class="keyword">int32</span>, name <span class="keyword">string</span>)</span> *<span class="title">services</span>.<span class="title">ProductModel</span></span> &#123;</span><br><span class="line">	<span class="keyword">return</span> &amp;services.ProductModel&#123;ProductID: id, ProductName: name&#125;</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">//降级处理函数，固定生成5个商品信息</span></span><br><span class="line"><span class="function"><span class="keyword">func</span> <span class="title">DefaultProducts</span><span class="params">(rsp <span class="keyword">interface</span>&#123;&#125;)</span></span> &#123;</span><br><span class="line">	models := <span class="built_in">make</span>([]*services.ProductModel, <span class="number">0</span>)</span><br><span class="line">	<span class="keyword">var</span> i <span class="keyword">int32</span></span><br><span class="line">	<span class="keyword">for</span> i = <span class="number">0</span>; i &lt; <span class="number">5</span>; i++ &#123;</span><br><span class="line">		models = <span class="built_in">append</span>(models, NewProduct(i+<span class="number">20</span>, <span class="string">"productName"</span>+strconv.Itoa(<span class="number">20</span>+<span class="keyword">int</span>(i))))</span><br><span class="line">	&#125;</span><br><span class="line">	result := rsp.(*services.ProductListResponse)</span><br><span class="line">	result.ProductList = models</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">//go-micro Wrapper中间件</span></span><br><span class="line"><span class="keyword">type</span> ProductWrapper <span class="keyword">struct</span> &#123;</span><br><span class="line">	client.Client</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">//Wrapper中间件的执行方法</span></span><br><span class="line"><span class="function"><span class="keyword">func</span> <span class="params">(this *ProductWrapper)</span> <span class="title">Call</span><span class="params">(ctx context.Context, req client.Request, rsp <span class="keyword">interface</span>&#123;&#125;, opts ...client.CallOption)</span> <span class="title">error</span></span> &#123;</span><br><span class="line">	cmdName := req.Service() + <span class="string">"."</span> + req.Endpoint()</span><br><span class="line">	config := hystrix.CommandConfig&#123;</span><br><span class="line">		Timeout: <span class="number">1000</span>,</span><br><span class="line">	&#125;</span><br><span class="line">	hystrix.ConfigureCommand(cmdName, config)</span><br><span class="line">	<span class="keyword">return</span> hystrix.Do(cmdName, <span class="function"><span class="keyword">func</span><span class="params">()</span> <span class="title">error</span></span> &#123;</span><br><span class="line">		<span class="keyword">return</span> this.Client.Call(ctx, req, rsp)</span><br><span class="line">	&#125;, <span class="function"><span class="keyword">func</span><span class="params">(e error)</span> <span class="title">error</span></span> &#123;</span><br><span class="line">		DefaultProducts(rsp)</span><br><span class="line">		<span class="keyword">return</span> <span class="literal">nil</span></span><br><span class="line">	&#125;)</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">//初始化Wrapper</span></span><br><span class="line"><span class="function"><span class="keyword">func</span> <span class="title">NewProductWrapper</span><span class="params">(c client.Client)</span> <span class="title">client</span>.<span class="title">Client</span></span> &#123;</span><br><span class="line">	<span class="keyword">return</span> &amp;ProductWrapper&#123;c&#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><code>func (this *ProductWrapper) Call(ctx context.Context, req client.Request, rsp interface{}, opts ...client.CallOption) error</code> Call 方法相当于拦截器，需要自己编写</p>
<p><code>hystrix.CommandConfig</code> 创建一个熔断器的配置 config</p>
<p><code>hystrix.ConfigureCommand(cmdName, config)</code>配置 command</p>
<p><code>hystrix.Do</code> Do 方法里有三个参数，第一个参数是 config 的名字；第二个参数是执行函数，发生熔断时会执行；第三个参数是降级函数，通常不会写太复杂</p>
<p><code>this.Client.Call(ctx, req, rsp)</code> 调用上级的 Call 方法</p>
<h3><span id="maingo">main.go</span></h3>
<p>只需在<code>micro.NewService</code>函数里加一个参数，<code>micro.WrapClient(wrappers.NewProductWrapper)</code>表示使用自己定义的 ProductWrapper 中间件及 Call 方法</p>

                

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